tax implications of withdrawing from a pension scheme early

Withdrawal of cash/shares from a pension scheme before retirement age - tax penalties. Any way to relieve the tax charge?

Before I get the usual lectures about the above being completely mad, I already know, and furtunately did not advise the person I am speaking to, to do this. I also know that pension advice needs to be done by an IFA rather than an accountant.

I do however want to update my knowledge of the tax rules on the above, and, rather annoyingly, my tax guide (Bloomsbury) doesn't have any details on this specific part of the taxation of pensions. I've tried searching the HMRC website, which again, predictably was useless. What I have managed to figure out is that there is a big income tax penalty (something like 55%) although logically, I would have thought this should be subject to capital gains tax. I can't find the rules on calculating this however, and just want to make sure I know what I'm talking about from the tax standpoint on this, as it is something I've never seen before, so if anyone could explain, or point me to the relevant HMRC guidance, it would be much much appreciated.